Biology subjects

Saumya, K. U.

Publications and source records attributed to Saumya, K. U..

6 recordsLinked to original sources

bioRxiv2023

Japanese Encephalitis Virus: A pan-proteome analysis for aggregation propensities and in vitro validation with Capsid anchor and 2K peptide

Japanese encephalitis infection is a vector-borne disease caused by the flavivirus Japanese encephalitis virus (JEV). It is responsible of severe brain infection in humans worldwide. Given the ubiquitous nature of complications and tropism associated with Japanese encephalitis (JE) infection, a holistic understanding of its molecular mechanism is essential. The phenomenon of abnormal protein aggregation into pathogenic amyloids is now increasingly linked to multiple human diseases, also known as Amyloidosis. Most are neurodegenerative disorders but amyloidosis is not restricted to a specific organ or tissue type. The overlap of viral protein aggregation with human pathologies remains limited and it is gaining momentum, especially after the devastating Covid-19 pandemic. Therefore, in this study we have examined the likelihood of aggregation for the entire collection of proteins in JEV. Multiple independent web server tools were employed to scan for potential amyloid prone-regions (APRs), and it was followed by in vitro validation using two JEV transmembrane domains, Capsid anchor and 2K peptides. These synthetic viral peptides were introduced to artificial aggregation-inducing conditions and then analyzed using a different dye-based assays and microscopy methods confirming amyloid-like fibril structure formation. We found these aggregates cytotoxic to human neuronal cell line and membrane damaging to human blood derived RBCs. The aggregation kinetics of both peptides is enhanced in the presence of artificial membrane models and seeds of self and diabetes hallmark protein Amylin. Our findings thereby strongly suggest the possibility of JEV protein aggregation playing a vital role in its pathogenesis, opening up a broad scope of future study. Also, the interplay between JEV protein aggregation and initiation/progression of other proteopathies is possible and needs further exploration. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=116 SRC="FIGDIR/small/556571v1_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@2956d0org.highwire.dtl.DTLVardef@28128org.highwire.dtl.DTLVardef@6d7faaorg.highwire.dtl.DTLVardef@d89f40_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2023

Met58 and di-acidic motif located at C-terminal region of SARS-CoV-2 ORF6 plays a crucial role in its structural conformations

Despite being mostly neglected in structural biology, the C-terminal Regions (CTRs) are studied to be multifunctional in humans as well as in viruses. Their role in cellular processes such as trafficking, protein-protein interactions, and protein-lipid interactions are known due to their structural properties. In our previous findings on SARS-CoV-2 Spike and NSP1 proteins, the C-terminal regions (CTRs) are observed to be disordered and experimental evidence showed a gain of structure properties in different physiological environments. In this line, we have investigated the structural dynamics of CTR (residues 38-61) of SARS-CoV-2 ORF6 protein, disrupting bidirectional transport between the nucleus and cytoplasm. Like Spike and NSP1-CTR, the ORF6-CTR is also disordered in nature but possesses gain of structure properties in minimal physiological conditions. As per studies, the residue such as Methionine at 58th position in ORF6 is critical for interaction with Rae1-Nup98. Therefore, along with M58, we have identified a few other mutations from the literature and performed extensive structure modelling and dynamics studies using computational simulations. The exciting revelations in CTR models provide evidence of its structural flexibility and possible capabilities to perform multifunctionality inside the host.

biophysics↗

bioRxiv2022

The aggregation potential of Zika virus proteome

The ability of human encoded soluble proteins to convert into amyloid fibrils is now recognized as a generic phenomenon in several human illnesses. Typically, such disease causal proteins/peptides consist of aggregation-prone regions (APR) that make them susceptible to misfolding and assemble into highly ordered {beta}-sheet rich fibrils, distinct from their native soluble state. Here, we show that the zika virus (ZIKV) consists of several such aggregation prone hotspots spread across its entire proteome. Using a combination of high-accuracy prediction tools, we identified APRs in both structural and non-structural proteins of ZIKV. Furthermore, we have experimentally validated the bioinformatic results by subjecting the ZIKV proteins and peptides to artificial aggregation inducing environment. Using a combination of dye-based assays (ThT and ANS) and microscopy techniques (HR-TEM and AFM), we further characterized the morphological features of amyloid-like fibrils. We found that Envelope domain III (EDIII) protein, NS1 {beta}-roll peptide, membrane-embedded signal peptide 2K, and cytosolic region of NS4B protein to be highly aggregating in the experimental setup. Our findings also pave the way for an extensive and detailed functional analysis of these predicted APRs in the future to enhance our understanding of the role played by amyloids in the pathogenesis of flavivirus. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=122 SRC="FIGDIR/small/485915v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@1bedf4dorg.highwire.dtl.DTLVardef@364676org.highwire.dtl.DTLVardef@14bf54aorg.highwire.dtl.DTLVardef@1d4fc19_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2021

Investigating the conformational dynamics of SARS-CoV-2 NSP6 protein with emphasis on non-transmembrane 91-112 & 231-290 regions

The NSP6 protein of SARS-CoV-2 is a transmembrane protein, with some regions lying outside the membrane. Besides, a brief role of NSP6 in autophagosome formation, this is not studied significantly. Also, there is no structural information available till date. Based on the prediction by TMHMM server for transmembrane prediction, it is found that the N-terminal residues (1-11), middle region residues (91-112) and C-terminal residues (231-290) lies outside the membrane. Molecular Dynamics (MD) simulations showed that NSP6 consisting of helical structures, whereas membrane outside lying region (91-112) showed partial helicity, which further used as model and obtain disordered type conformation after 1.5 microsecond. Whereas, the residues 231-290 has both helical and beta sheet conformations in its structure model. A 200ns simulations resulted in the loss of beta sheet structures, while helical regions remained intact. Further, we have characterized the residue 91-112 by using reductionist approaches. The NSP6 (91-112) was found disordered like in isolation, which gain helical conformation in different biological mimic environmental conditions. These studies can be helpful to study NSP6 (91-112) interactions with host proteins, where different protein conformation might play significant role. The present study adds up more information about NSP6 protein aspect, which could be exploited for its host protein interaction and pathogenesis. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=123 SRC="FIGDIR/small/451329v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@1b6e8aborg.highwire.dtl.DTLVardef@165564eorg.highwire.dtl.DTLVardef@551f7org.highwire.dtl.DTLVardef@1485518_HPS_FORMAT_FIGEXP M_FIG C_FIG The schematic representation of NSP6 membrane topology and conformational dynamics of residue 91-112. The N-terminal and C-terminal are shown in cytoplasmic side based on the experimental evidence on coronaviruses reported by Oostra et al., 2008. The membrane anchoring domain are shown based on the TMHMM server prediction.

biophysics↗

bioRxiv2021

Amyloidogenic proteins in the SARS-CoV and SARS-CoV-2 proteomes

The phenomenon of protein aggregation is associated with a wide range of human diseases. Our knowledge on the aggregation behaviour of viral proteins, however, is still rather limited. Here, we investigated this behaviour in the the SARS-CoV and SARS-CoV-2 proteomes. An initial analysis using a panel of sequence-based predictors suggested the presence of multiple aggregation-prone regions in these proteomes, and revealed an enhanced aggregation propensity in some SARS-CoV-2 proteins. We then studied the in vitro aggregation of predicted aggregation-prone SARS-CoV-2 proteins, including the signal sequence peptide and fusion peptide 1 of the spike protein, a peptide from the NSP6 protein (NSP6-p), the ORF10 protein, and the NSP11 protein. Our results show that these peptides and proteins form aggregates via a nucleation-dependent mechanism. Moreover, we demonstrated that the aggregates of NSP11 are toxic to mammalian cell cultures. These findings provide evidence about the aggregation of proteins in the SARS-CoV-2 proteome. SignificanceThe aggregation of proteins is linked with human disease in a variety of ways. In the case of viral infections, one could expect that the aberrant aggregation of viral proteins may damage the host cells, and also that viral particles may trigger the misfolding and aggregation of host proteins, resulting in damage to the host organism. Here we investigate the aggregation propensity of SARS-CoV-2 proteins and show that many of them can form aggregates that are potentially cytotoxic. In perspective, these results suggest that a better understanding of the effects of viruses on the human protein homeostasis system could help future therapeutic efforts.

biophysics↗

bioRxiv2020

Zika Virus Capsid Anchor Forms Cytotoxic Amyloid-like Fibrils

Capsid-anchor (CA) of Zika virus (ZIKV) is a small, single-pass transmembrane sequence that separates the capsid (C) protein from downstream pre-membrane (PrM) protein. During ZIKV polyprotein processing, CA is cleaved-off from C and PrM and left as a membrane-embedded peptide. CA plays an essential role in the assembly and maturation of the virus. However, its independent folding behavior is still unknown. Since misfolding and aggregation propensity of transmembrane proteins are now increasingly recognized and has been linked to several proteopathic disorders. Therefore, in this study, we investigated the amyloid-forming propensity of CA at physiological conditions. We observed aggregation behavior of CA peptide using dyebinding assays and ThT kinetics. The morphological analysis of CA aggregates explored by high-resolution microscopy (TEM and AFM) revealed characteristic amyloid-like fibrils. Further, the effect on mammalian cells exhibited the cytotoxic nature of the CA amyloid-fibrils. Our findings collectively shed light on the amyloidogenic phenomenon of flaviviral protein, which may contribute to their infection. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=80 SRC="FIGDIR/small/381988v1_ufig1.gif" ALT="Figure 1"> View larger version (20K): org.highwire.dtl.DTLVardef@940e19org.highwire.dtl.DTLVardef@29a854org.highwire.dtl.DTLVardef@ea22e1org.highwire.dtl.DTLVardef@197f9d7_HPS_FORMAT_FIGEXP M_FIG Schematic representation of Zika virus Capsid anchor forming amyloid aggregates with cytotoxic and hemolytic properties. C_FIG

biochemistry↗